This application claims Paris Convention priority of DE 199 20 900 filed May 6, 1999 the complete disclosure of which is hereby incorporated by reference.
The invention concerns a packaging machine comprising a folding box transporting means and a closing device for aligning and inserting the closure flaps of a folding box, wherein the closing device bears at least one closing tool which rotates via a drive and a gearing while maintaining its orientation.
A packaging machine for packing a product into a folding box usually has an endless circulating folding box chain and an endless circulating transport device for the products, e.g. a so-called product chain. The motions of the folding box chain and the product chain are synchronized such that the product can be inserted into the folding box transverse to the direction of motion of the chains. After insertion of the products, the lateral closure flaps of the folding box must be aligned and inserted in a subsequent operating step using a so-called closing device comprising one or more closing tools of conventional construction which carry out a circulating rotary motion in a plane essentially parallel to the surface of the folding box chain while maintaining their orientation relative to the folding box chain and therefore substantially exercising a translational motion along a closed curve. The drive belt or a drive chain often used in packaging machines is normally used as a drive element for this motion and drives a belt wheel whose rotary motion is translated via a crank gear into the above mentioned circulating motion of the closing tools. Practice has shown that the crank is susceptible to malfunction and, in particular, to jamming thereby impairing or even seriously disturbing operation of the packaging machine. Moreover, a crank gear has relatively large moving masses on long lever arms which generate large inertial forces at high packaging machine cycle times and associated high crank gear speeds leading to very unsteady and imprecise motion of the closing tools.
It is the underlying purpose of the invention to generate a closing device in a packaging machine of the mentioned kind which guarantees precise motion of the closing tools even at high packaging machine cycle frequencies.
This object is achieved in a packaging machine of the mentioned kind by using a planetary gearing. This gearing can be compact in structure and exhibit inertial forces during operation of the planetary gearing which are considerably smaller than those of a crank gearing, such that precise closing motion of the closing tools can be achieved even for high planetary gear speeds.
The planetary gearing preferably comprises a rotary driven planetary support with an intermediate wheel borne thereon which turns on a stationary sun wheel and drives a drive wheel rotatably borne on the planetary support whose output shaft has a holder for the closing tool. To enable easy replacement of the closing tool(s) when required, the closing tools are preferably mounted to the holder via a releasable clamping device.
In accordance with a preferred embodiment of the invention, the drive motion of the toothed belt or chain is transmitted to a hollow drive shaft on which the drive belt wheel is integrally formed or to which it is mounted. The hollow drive shaft is rotatably borne in the machine tool and is connected to and rotates without slipping along with an intermediate shaft coaxially disposed therein. The hollow drive shaft and the intermediate shaft thereby rotate as a unit. The planetary support borne by the intermediate shaft is rotatably driven via the toothed belt.
The closing device must be adapted to format changes in the folding boxes to be closed. Towards this end, the intermediate shaft is disposed in the hollow drive shaft in an axially displaceable fashion such that axial relative adjustment can change the vertical position of the planetary support and thereby of the closing tools. Adjustment of the planetary support must be accompanied by a corresponding axial adjustment of the sun wheel. In accordance with the invention, this can be achieved in a structurally advantageous manner when the intermediate shaft is also a hollow shaft, wherein a supporting bar extends through the intermediate shaft and bears the sun wheel at one end thereof. In a further development of the invention, an adjustment device can displace the planetary gearing as a unit along with the intermediate shaft and the supporting bar in an axial direction relative to the hollow drive shaft which is, in turn, borne for rotation without axial displacement in the packaging machine. The adjustment device can thereby be e.g. a spindle nut unit which can be adjusted manually or by a motor-drive and which securely maintains the set position.
Further details and features of the invention can be extracted from the following description of an embodiment with reference to the drawings.